I started using Fedora Silverblue on a tablet, seems to work fine so far, but requiring a reboot in order to install new system packages is a bit cumbersome and the process itself takes a while, but ordinary Fedora also doesn’t win any races when asked to install a new package

I think switching to FCOS or Flatcar on servers that just use containers makes sense. Since it lessens the burden of administrating the base system itself. Using butan/ignition might be unusual at first, but it also allows to put the base system configuration into a git repo, and makes initial provisioning using ansible or similar unnecessary. The rest of the system and services can be managed via portainer or similar software.

I also do not have long term experience with FCOS, but the advertised features of auto-update, rolling-release, focus on security and stability makes it a good fit for container servers, IMO.

An alternative to Debian on servers might also be Apline Linux. Which also has more a focus on network devices, but some people use it on a desktop as well.

If you have many different systems, and just want to learn to operate them all, maybe NixOS might be interesting. Using flakes, you can configure multiple machines from just one repo, and share configurations between them. But getting up to speed on NixOS might not be so easy, it has a steep learning curve.